Deposit-control fuel additives effectively control deposits in carburetors, valves and fuel injectors of engine intake systems. Aminated polybutenes are widely employed as deposit control fuel additives. Aminated polybutenes are produced commercially by one of three prior art processes which involve the reaction of chlorinated polybutene with an amine compound to produce a polybutene amine. These prior art processes, however, are characterized by the separation of undesirable side products, the creation of a large volume of contaminated aqueous waste streams and the requirement to remove alcohols or ammonia from the excess amine reactant.
U.S. Pat. No. 3,671,511, represents one of the primary processes employed to produce polybutene amines today. It involves the reaction of chlorinated polybutene with an excess of polyamine, stripping the excess amine under vacuum, adding aromatic solvent to dilute the reaction mixture, and neutralizing the reaction mixture with aqueous sodium hydroxide. This step forms an emulsion which is broken by adding butanol. The phases are separated and the organic layer is washed several times using water, stripped of butanol and dried, then diluted with the desired solvent. This process has many potential disadvantages. One mole of excess amine per mole of reacted chlorinated polybutene is not recovered during neutralization and ultimately is discarded in an aqueous salt solution. This results in the loss of a valuable raw material. The large volume of aqueous waste stream generated contains salt, amine, traces of aromatic solvent and butanol. This waste stream represents a potential disposal problem. The butanol adds to the cost of the process since it cannot be totally recovered, and the necessity of performing multiple washes increases cycle time and manufacturing costs.
U.S. Pat. No. 3,454,555 describes another frequently used process to prepare polybutene amines and describes a system which overcomes many process-related problems associated with aqueous separation/water washing, the use of butanol and the loss of neutralized amine. It has a different potential problem, however, which can render its product unacceptable to the customer. This process involves the reaction of an excess of polyamine with a chlorinated polybutene in the presence of sodium carbonate. When the reaction is completed, the excess amine and water of neutralization are removed by vacuum stripping, the reaction mixture is diluted with solvent and filtered to remove inorganic salts, and the product is then stripped of excess solvent to the desired basic nitrogen level. The potential disadvantages of this process are that: (1) the carbon dioxide produced as a by-product reacts with the excess amine and the product to produce other by-products; and 2) the excess amine and water require further processing (separation) in order to reuse/recycle the excess amine. The above noted by-products are insoluble in the product and, with time, precipitate out to form a solid phase which creates many problems for the customer. Removal of this solid phase adds substantial cost.
U.S. Pat. No. 5,346,965 describes another process used to produce polybutene amines. This process avoids the problems of aqueous waste streams and undesirable side-products left in the product. This process utilizes an alkali metal, an alkaline earth metal alkoxide or an amide to neutralize the amine hydrochloride which forms as a by-product. A potential disadvantage of this process is that highly reactive and potentially hazardous alkali metals, alkaline earth metal alkoxides or amides have to be used, and volatile and flammable alcohols or ammonia which are formed during the process have to be removed from the excess amine reactant and product.